1. Field of the Invention
The present invention relates to an improvement in the method of cleaning semiconductor wafers (hereinafter referred to, for brevity, as "wafers").
2. Description of the Related Art
Wafers such as silicon wafers, after they are polished, are subjected to chemical cleaning with the use of a solution of ammonium hydroxide (NH.sub.4 OH), hydrogen peroxide (H.sub.2 O.sub.2) and water (H.sub.2 O) to remove particles and organic compounds. The cleaning with NH.sub.4 OH--H.sub.2 O.sub.2 --H.sub.2 O solution, however, degrades the surface roughness (micro-roughness) of the polished wafers due to an etching reaction effected thereon. It is known that the degradation of micro-roughness not only degrades the limit of particles disposed on a wafer surface which are detected by a particle counter using the scattering of a laser beam, but also lowers the breakdown voltage of an oxide film formed on the wafer which might eventually affect the yield and performance of semiconductor devices formed on this wafer surface.